Method for improving efficiency of a refrigerator appliance during a defrost cycle

ABSTRACT

A method for operating a refrigerator appliance during a defrost cycle of the refrigerator appliance is provided. The method includes deactivating a compressor of the refrigerator appliance at a beginning or commencement of the defrost cycle until a predetermined period of time elapses or a chilled chamber of the refrigerator appliance rises to a preselected temperature. The method can improve an energy efficiency of the refrigerator appliance.

FIELD OF THE INVENTION

The present subject matter relates generally to refrigerator appliances.

BACKGROUND OF THE INVENTION

Consumer refrigerator appliances generally utilize a relatively simple vapor compression refrigeration apparatus that includes a compressor, a condenser, an expansion device, and an evaporator connected in series. The system is charged with a refrigerant such as R-134a. During operation, pressurized liquid refrigerant from the compressor and condenser enters the expansion device. Upon exiting the expansion device and entering the evaporator, the refrigerant drops in pressure and changes phase from a liquid to a gas.

Due to the pressure drop and phase change of the refrigerant in the evaporator, heat from a chilled chamber of the refrigerator appliance (e.g., a freezer chamber or a fresh food chamber) is transferred to the refrigerant within the evaporator. During the heat transfer, water vapor within the chilled chamber can freeze upon contact with the evaporator and create a frost buildup. Such frost buildup can grow in size until it negatively affects operation of the refrigerator appliance. Accordingly, certain refrigerator appliance include a defrost cycle during which such frost buildup melts and is removed from the evaporator.

Defrost cycles can include a pre-chill portion at a beginning of the defrost cycle during which the vapor compression refrigeration apparatus operates to cool the chilled chamber below a certain threshold. The pre-chill portion can provide a buffer that prevents overheating of the chilled chamber during the defrost cycle. Due to the high energy demands of the vapor compression refrigeration apparatus, the pre-chill portion of the defrost cycle can utilize a significant amount of the total energy consumed by the refrigerator appliance during the defrost cycle.

Determining when to initiate a defrost cycle can be based upon various factors. Generally, defrost cycles are initiated without considering the temperature of the chilled chamber; however, the chilled chamber may already be at a relatively low temperature prior to initiating the defrost cycle. Thus, the pre-chill portion of the defrost cycle may be totally unnecessary or unnecessarily long such that the refrigerator appliance wastes valuable energy during the pre-chill portion of the defrost cycle.

Accordingly, a refrigerator appliance with features for improved efficiency during a defrost cycle of the refrigerator appliance would be useful.

BRIEF DESCRIPTION OF THE INVENTION

The present subject matter provides a method for operating a refrigerator appliance during a defrost cycle of the refrigerator appliance. The method includes deactivating a compressor of the refrigerator appliance at a beginning or commencement of the defrost cycle until a predetermined period of time elapses or a chilled chamber of the refrigerator appliance rises to a preselected temperature. The method can improve an energy efficiency of the refrigerator appliance. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.

In a first exemplary embodiment, a refrigerator appliance is provided. The refrigerator appliance includes a cabinet that defines a chilled chamber for receipt of food items for storage. A compressor is positioned within the cabinet. An evaporator heater is positioned within the chilled chamber of the cabinet. The refrigerator appliance also includes a controller that is in operative communication with the compressor and the evaporator heater. The controller is configured for initiating a defrost cycle of the refrigerator appliance and deactivating the compressor for a predetermined period of time or until the chilled chamber of the cabinet rises to a preselected temperature at a commencement of the defrost cycle. The controller is also configured for operating the evaporator heater during the defrost cycle after the step of deactivating.

In a second exemplary embodiment, a method for operating a refrigerator appliance during a defrost cycle is provided. The refrigerator appliance has a cabinet that defines a chilled chamber, a compressor, and an evaporator heater. The method includes deactivating the compressor of the refrigerator appliance at a commencement of the defrost cycle, maintaining the compressor of the refrigerator appliance in a deactivated state until a predetermined time period of time elapses or until the chilled chamber of the refrigerator appliance rises to a preselected temperature, activating the compressor of the refrigerator appliance during the defrost cycle after the step of maintaining, and operating the evaporator heater of the refrigerator appliance during the defrost cycle after the step of activating.

In a third exemplary embodiment, a method for operating a refrigerator appliance during a defrost cycle is provided. The refrigerator appliance has a cabinet that defines a chilled chamber, a compressor, and an evaporator heater. The method include deactivating the compressor of the refrigerator appliance for a predetermined period of time at a commencement of the defrost cycle. The method also includes operating the evaporator heater of the refrigerator appliance during the defrost cycle after the step of deactivating.

In a fourth exemplary embodiment, a method for operating a refrigerator appliance during a defrost cycle is provided. The refrigerator appliance has a cabinet that defines a chilled chamber, a compressor, and an evaporator heater. The method include deactivating the compressor of the refrigerator appliance until the chilled chamber of the refrigerator appliance rises to a preselected temperature at a commencement of the defrost cycle. The method also includes operating the evaporator heater of the refrigerator appliance during the defrost cycle after the step of deactivating.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 provides a front, elevation view of a refrigerator appliance according to an exemplary embodiment of the present subject matter.

FIG. 2 provides a schematic view of a refrigeration system of the refrigerator appliance of FIG. 1.

FIG. 3 provides a schematic view of the refrigerator appliance of FIG. 1 with a controller provided for operating components of the refrigeration system of the refrigerator appliance.

FIG. 4 provides a graphical representation of an exemplary embodiment of a defrost cycle of the refrigerator appliance of FIG. 1 as may be implemented by the controller of the refrigerator appliance.

FIGS. 5-8 illustrate methods for operating a refrigerator appliance during a defrost cycle of the refrigerator appliance according to exemplary embodiments of the present subject matter.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 depicts a refrigerator appliance 10 according to an exemplary embodiment of the present subject matter. Refrigerator appliance 10 incorporates a sealed refrigeration system 60 (FIG. 2). It should be appreciated that the term “refrigerator appliance” is used in a generic sense herein to encompass any manner of refrigeration appliance, such as a freezer, refrigerator/freezer combination, and any style or model of conventional refrigerator.

In the exemplary embodiment shown in FIG. 1, refrigerator appliance 10 is depicted as an upright refrigerator having a cabinet or casing 12 that defines a number of internal storage compartments or chilled chambers. In particular, refrigerator appliance 10 includes upper fresh-food compartments 14 having doors 16 and lower freezer compartment 18 having upper drawer 20 and lower drawer 22. The drawers 20, 22 are “pull-out” drawers in that they can be manually moved into and out of the freezer compartment 18 on suitable slide mechanisms.

FIG. 2 is a schematic view of refrigerator appliance 10 including a sealed refrigeration system 60 according to an exemplary embodiment of the present subject matter. In particular, a machinery compartment 62 contains components for executing a known vapor compression cycle for cooling air. The components include a compressor 64, a condenser 66, an expansion device 68, and an evaporator 70 connected in series and charged with a refrigerant. Collectively, the vapor compression cycle components, associated fans, and associated compartments are sometimes referred to as a sealed refrigeration system operable to force cold air through compartments 14 and 18 (FIG. 1).

Refrigeration system 60 depicted in FIG. 2 is provided by way of example only. Thus, it is within the scope of the present subject matter for other configurations of the refrigeration system to be used as well. As will be understood by those skilled in the art, refrigeration system 60 may include additional components, e.g., at least one additional evaporator, compressor, expansion device, and/or condenser. As an example, refrigeration system 60 may include two evaporators.

Within refrigeration system 60, gaseous refrigerant flows into compressor 64, which operates to increase the pressure of the refrigerant. Such compression of the refrigerant raises its temperature, which is lowered by passing the gaseous refrigerant through condenser 66. Within condenser 66, heat exchange with ambient air takes place so as to cool the refrigerant and cause the refrigerant to condense to a liquid state. A condenser fan 72 is used to pull air across condenser 66, as illustrated by arrows A_(C), so as to provide forced convection for a more rapid and efficient heat exchange between the refrigerant within condenser 66 and the ambient air. Thus, as will be understood by those skilled in the art, increasing air flow across condenser 66 can, e.g., increase the efficiency of condenser 66 by improving cooling of the refrigerant contained therein.

An expansion device (e.g., a valve, capillary tube, or other restriction device) 68 receives liquid refrigerant from condenser 66. From expansion device 68, the liquid refrigerant enters evaporator 70. Upon exiting expansion device 68 and entering evaporator 70, the liquid refrigerant drops in pressure and vaporizes. Due to the pressure drop and phase change of the refrigerant, evaporator 70 is cool relative to compartments 14, 18 of refrigerator appliance 10. As such, cooled air is produced and refrigerates compartments 14, 18 of refrigerator appliance 10. Thus, evaporator 70 is a type of heat exchanger which transfers heat from air passing over evaporator 70 to refrigerant flowing through evaporator 70. An evaporator fan 76 is positioned within compartments 14 and/or 18. Evaporator fan 76 is provided for urging air across evaporator 70 and cycling air within compartments 14 and/or 18. An evaporator heater 74 is positioned adjacent evaporator 70 for heating evaporator 70 and melting ice located thereon during a defrost cycle of refrigerator appliance 10 as discussed in greater detail below.

FIG. 3 provides a schematic view of refrigerator appliance 10. Refrigerator appliance 10 includes a controller 80 that is operatively coupled or in communication with components of refrigeration system 60 (FIG. 2) including compressor 64, evaporator heater 74, evaporator fan 76, and condenser fan 72 such that controller 80 can operate the components. Controller 80 is also in communication with a temperature sensor 82, e.g., a thermocouple or thermistor. Temperature sensor 82 may be positioned in one of compartments 14 or 18 (FIG. 2). Controller 80 may receive a signal from temperature sensor 82 that corresponds to a temperature of compartments 14 or 18. Controller 80 may also include an internal timer for calculating elapsed time periods.

Controller 80 may include a memory and one or more microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of refrigerator appliance 10. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor.

Controller 80 may be positioned in a variety of locations throughout refrigerator appliance 10. Input/output (“I/O”) signals may be routed between controller 80 and various operational components of refrigerator appliance 10. The components of refrigeration system 60 may be in communication with controller 150 via one or more signal lines or shared communication busses.

FIG. 4 provides a graphical representation of an exemplary embodiment of a defrost cycle or defrost sequence 400 of refrigerator appliance 10 (FIG. 1). Defrost cycle 400 shown in FIG. 4 may be implemented by controller 80 of refrigerator appliance 10. Defrost cycle 400 includes several distinct steps. In particular, defrost cycle 400 includes (in sequential order) an initial off step 410, a pre-chill step 420, a defrost step 430, a dwell step 440, a fan delay step 450, a recovery step 460, and a final off step 470. As will be understood by those skilled in the art, defrost cycle 400 shown in FIG. 4 is provided by way of example only and is not intended to limit the present subject matter in any manner. Thus, controller 80 of refrigerator appliance 10 can implement alternative defrost cycles with various combinations of the steps described above or suitable additional steps.

Prior to defrost cycle 400, refrigeration system 60 (FIG. 2) of refrigerator appliance 10 (FIG. 1) may or may not be running as shown with the dashed lines in FIG. 4. Initial off step 410 begins or commences defrost cycle 400. During initial off step 410, controller 80 deactivates refrigeration system 60, e.g., compressor 64, evaporator fan 76, and/or condenser fan 72. As shown in FIG. 4, energy consumption of refrigerator appliance 10 can be minimized for defrost cycle 400 during initial off step 410 such that an energy efficiency of refrigerator appliance 10 is improved. Initial off step 410 is discussed in greater detail below.

After initial off step 410, defrost cycle 400 enters pre-chill step 420. During pre-chill step 420, controller 80 activates refrigeration system 60, e.g., compressor 64, evaporator fan 76, and/or condenser fan 72, in order to reduce a temperature of compartments 14 and/or 18. For example, refrigeration system 60 can reduce the temperature of fresh food compartment 14 to about thirty-six, thirty-four, or thirty-two degrees Fahrenheit or any other suitable temperature during pre-chill step 420. In alternative exemplary embodiments, refrigeration system 60 can reduce the temperature of freezer chamber 18 to about negative twenty, negative ten, or negative five degrees Fahrenheit or any other suitable temperature during pre-chill step 420. Such pre-chilling can assist with hindering or preventing overheating of compartments 14 and/or 18 and food contents therein during subsequent steps of defrost cycle 400.

After pre-chill step 420, defrost cycle 400 enters defrost step 430. During defrost step 430, controller 80 turns off compressor 64, evaporator fan 76, and/or condenser fan 72 and turns on evaporator heater 74. When evaporator heater 74 is activated during defrost step 430, ice disposed on evaporator 70 melts thereby improving performance of refrigeration appliance 10 by permitting evaporator 70 to operate more effectively. After defrost step 430, defrost cycle 400 enters dwell step 440. During dwell step 440, controller 80 turns off refrigeration system 60 in order to permit water generated during defrost step 430 to drain off evaporator 70 and also to permit evaporator 70 to cool.

After dwell step 440, defrost cycle 400 enters fan delay step 450. During fan delay step 450, controller 80 activates compressor 64 and/or condenser fan 72 but does not turn on evaporator fan 76. Compressor 64 circulates refrigerant heated during defrost step 430 through refrigeration system 60, and condenser fan 72 assists with cooling the heated refrigerant within condenser 66. By not turning on evaporator fan 76, evaporator fan 76 does not circulate heated air from evaporator 70 within compartments 14 and/or 18.

After fan delay step 450, the defrost cycle enters recovery step 460. During recovery step 460, controller 80 activates refrigeration system 60, e.g., compressor 64, evaporator fan 76, and/or condenser fan 72, in order to cool compartments 14 and 18. During defrost step 430, operation of evaporator heater 74 heats up compartments 14 and 18 and food items located therein. Recovery step 460 is configured for returning refrigerator appliance 10 to its steady state operating condition after defrost cycle 400. Thus, the refrigerator appliance 10 has recovered after defrost step 430 and is in its normal, steady state operating condition in final off step 470 such that controller 80 can deactivate refrigeration system 60.

FIGS. 5 and 6 illustrate methods 500 (FIGS. 5) and 600 (FIG. 6) for operating a refrigerator appliance, e.g., refrigerator appliance 10 (FIG. 1), during a defrost cycle, e.g., defrost cycle 400 (FIG. 4), according to exemplary embodiments of the present subject matter. Methods 500 and 600 can improve an energy efficiency of refrigerator appliance 10. For example, methods 500 and 600 provide a defrost cycle with initial off step 410 described above. Methods 500 and 600 may be implemented or carried out by controller 80.

Method 500 is shown in FIG. 5. At step 510, controller 80 deactivates compressor 64 of refrigerator appliance 10 at a commencement or beginning of a defrost cycle. Thus, each defrost cycle of refrigerator appliance 10 begins with controller 64 deactivating compressor 64. At step 510, controller 80 can deactivate compressor 64 for a predetermined period of time (shown with P_(t) in FIG. 4) such as, e.g., fifteen minutes, thirty minutes, one hour, two hours, between about one hour and about two hours, or any other suitable period of time. Conversely, controller 80 can also deactivate compressor 64 during step 510 until compartments 14 and/or 18 reach a preselected temperature. The preselected temperature may be any suitable valve. For example, the preselected temperature may be about thirty, about thirty-two, about thirty-four degrees Fahrenheit, or between about thirty and thirty-four degrees Fahrenheit. As an example, controller 80 may receive a signal from temperature sensor 82 in order to monitor the temperature of compartments 14 and/or 18.

At step 520, controller 80 operates evaporator heater 74 of refrigerator appliance 10 during the defrost cycle after step 510. Operating evaporator heater 74 during step 520 can assist with melting and removal of ice and frost from evaporator 70.

Method 500 may include additional steps, e.g., controller 80 may activate compressor 64 during the defrost cycle, after step 510 and prior to step 520. In such a manner, compressor 64 can assist with cooling compartments 14 and/or 18, e.g., to about negative ten degrees Fahrenheit, in order prevent compartments 14 and/or 18 from overheating when evaporator heater 74 is operating during step 520. Controller 80 can also deactivate evaporator fan 76 for the period of time at the commencement of the defrost cycle at step 510.

Method 500 can improve an energy efficiency of refrigerator appliance 10. By deactivating compressor 64 at the start of the defrost cycle, refrigerator appliance 10 can avoid unnecessary pre-chilling of compartments 14 and/or 18. For example, if compressor 64 is running just prior to the start of the defrost cycle, compartments 14 and/or 18 may be relatively cool such that immediately entering the pre-chill step would be inefficient. Thus, deactivating compressor 64 can permit compartments 14 and/or 18 to warm prior to the pre-chill step such that the pre-chill step is more effective and energy efficient relative to a defrost cycle without step 510. Like method 500, method 600 can improve an energy efficiency of refrigerator appliance 10.

Method 600 is shown in FIG. 6. At step 610, controller 80 deactivates compressor 64 of refrigerator appliance 10 at a commencement or beginning of a defrost cycle. Thus, each defrost cycle of refrigerator appliance 10 begins with controller 64 deactivating compressor 64. At step 620, controller 80 maintains compressor 64 in a deactivated state such that compressor 64 is not operating. Controller 80 maintains compressor 64 in the deactivated state until a predetermined time period of time elapses or until compartments 14 and/or 18 of refrigerator appliance 10 rise to a preselected temperature. The predetermined period of time may be any suitable period of time. For example, the predetermined period of time may be about fifteen minutes, about thirty minutes, about one hour, about two hours, between about one hour and about two hours, or any other suitable period of time. Similarly, the preselected temperature may be any suitable valve. For example, the preselected temperature may be about thirty, about thirty-two, about thirty-four degrees Fahrenheit, or between about thirty and about thirty-four degrees Fahrenheit.

At step 630, controller 80 operates evaporator heater 74 of refrigerator appliance 10 during the defrost cycle and after steps 610 and 620. Operating evaporator heater 74 during step 630 can assist with melting and removal of ice and frost from evaporator 70.

Method 600 may include additional steps, e.g., controller 80 may activate compressor 64 during the defrost cycle, after step 620, and prior to step 630. In such a manner, compressor 64 can assist with cooling compartments 14 and/or 18, e.g., to about negative ten degrees Fahrenheit, in order prevent compartments 14 and/or 18 from overheating when evaporator heater 74 is operating during step 630. Controller 80 can also deactivate evaporator fan 76 at the commencement of the defrost cycle at step 610.

Like method 500, method 600 can improve an energy efficiency of refrigerator appliance 10. By deactivating compressor 64 at the start of the defrost cycle, refrigerator appliance 10 can avoid unnecessary pre-chilling of compartments 14 and/or 18.

FIGS. 7 and 8 illustrate methods 700 (FIGS. 7) and 800 (FIG. 8) for operating a refrigerator appliance, e.g., refrigerator appliance 10 (FIG. 1), during a defrost cycle, e.g., the defrost cycle shown in FIG. 4, according to exemplary embodiments of the present subject matter. Like method 500 (FIG. 5) and method 600 (FIG. 6), methods 700 and 800 can improve an energy efficiency of refrigerator appliance 10. Methods 700 and 800 may be implemented or carried out by controller 80.

Methods 700 and 800 are substantially similar to method 500. However, in method 700, controller 80 deactivates compressor 64 of refrigerator appliance 10 for a period of time at a commencement or beginning of a defrost cycle. Thus, in method 700, each defrost cycle of refrigerator appliance 10 begins with controller 64 deactivating compressor 64 of the period of time. Conversely, in method 800, controller 80 deactivates compressor 64 at a commencement or beginning of a defrost cycle until compartments 14 and/or 18 reach a preselected temperature. Thus, in method 800, each defrost cycle of refrigerator appliance 10 begins with controller 64 deactivating compressor 64 until compartments 14 and/or 18 reach the preselected temperature.

As will be understood by those skilled in the art, controller 80 can implement method 700 or method 800 or both simultaneously. Thus, controller 80 can deactivate compressor 64 for a period of time at a commencement or beginning of a defrost cycle as in method 700, or controller 80 can deactivate compressor 64 until compartments 14 and/or 18 reach the preselected temperature at the commencement or beginning of the defrost cycle as in method 800. Alternatively, controller 80 can deactivate compressor 64 until compartments 14 and/or 18 reach the preselected temperature or for the period of time at the commencement or beginning of the defrost cycle, whichever occurs first.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A refrigerator appliance, comprising: a cabinet that defines a chilled chamber for receipt of food items for storage; a compressor positioned within said cabinet; an evaporator heater positioned within the chilled chamber of said cabinet; and a controller in operative communication with said compressor and said evaporator heater, said controller configured for: initiating a defrost cycle of the refrigerator appliance; deactivating said compressor for a predetermined period of time or until the chilled chamber of said cabinet rises to a preselected temperature at a commencement of the defrost cycle; and operating said evaporator heater during the defrost cycle after said step of deactivating.
 2. The refrigerator appliance of claim 1, wherein said controller is further configured for activating said compressor during the defrost cycle after said step of deactivating and prior to said step of operating.
 3. The refrigerator appliance of claim 2, wherein the chilled chamber of said cabinet drops to about negative ten degrees Fahrenheit during said step of activating.
 4. The refrigerator appliance of claim 1, wherein the preselected temperature is less than about thirty-four degrees Fahrenheit.
 5. The refrigerator appliance of claim 1, wherein the predetermined period of time is less than about two hours.
 6. The refrigerator appliance of claim 1, further comprising an evaporator fan positioned within the chilled chamber of said cabinet, said controller further configured for switching off the evaporator fan of the refrigerator appliance for the predetermined period of time or until the chilled chamber of said cabinet rises to the preselected temperature at the commencement of the defrost cycle.
 7. A method for operating a refrigerator appliance during a defrost cycle, the refrigerator appliance having a cabinet that defines a chilled chamber, a compressor, and an evaporator heater, the method comprising: deactivating the compressor of the refrigerator appliance at a commencement of the defrost cycle; maintaining the compressor of the refrigerator appliance in a deactivated state until a predetermined period of time elapses or until the chilled chamber of the refrigerator appliance rises to a preselected temperature; activating the compressor of the refrigerator appliance during the defrost cycle after said step of maintaining; and operating the evaporator heater of the refrigerator appliance during the defrost cycle after said step of activating.
 8. The method of claim 7, wherein the chilled chamber of the refrigerator appliance drops to about negative ten degrees Fahrenheit during said step of activating.
 9. The method of claim 7, wherein the preselected temperature is less than about thirty-four degrees Fahrenheit.
 10. The method of claim 7, wherein the predetermined period of time is less than about two hours.
 11. A method for operating a refrigerator appliance during a defrost cycle, the refrigerator appliance having a cabinet that defines a chilled chamber, a compressor, and an evaporator heater, the method comprising: deactivating the compressor of the refrigerator appliance for a predetermined period of time at a commencement of the defrost cycle; and operating the evaporator heater of the refrigerator appliance during the defrost cycle after said step of deactivating.
 12. The method of claim 11, further comprising activating the compressor of the refrigerator appliance during the defrost cycle after said step of deactivating and prior to said step of operating.
 13. The method of claim 12, wherein the chilled chamber of the refrigerator appliance drops to about negative ten degrees Fahrenheit during said step of activating.
 14. The method of claim 11, wherein the predetermined period of time is less than about two hours.
 15. The method of claim 11, wherein the refrigerator appliance further includes an evaporator fan, the method further comprising switching off the evaporator fan of the refrigerator appliance for the predetermined period of time at the commencement of the defrost cycle.
 16. A method for operating a refrigerator appliance during a defrost cycle, the refrigerator appliance having a cabinet that defines a chilled chamber, a compressor, and an evaporator heater, the method comprising: deactivating the compressor of the refrigerator appliance until the chilled chamber of the refrigerator appliance rises to a preselected temperature at a commencement of the defrost cycle; and operating the evaporator heater of the refrigerator appliance during the defrost cycle after said step of deactivating.
 17. The method of claim 16, wherein the preselected temperature is less than about thirty-four degrees Fahrenheit.
 18. The method of claim 16, further comprising activating the compressor of the refrigerator appliance during the defrost cycle after said step of deactivating and prior to said step of operating.
 19. The method of claim 18, wherein the chilled chamber of the refrigerator appliance drops to about negative ten degrees Fahrenheit during said step of activating.
 20. The method of claim 16, wherein the refrigerator appliance further includes an evaporator fan, the method further comprising switching off the evaporator fan of the refrigerator appliance until the chilled chamber of the refrigerator appliance rises to the preselected temperature at the commencement of the defrost cycle. 